DOC: Fix typo in to_html and to_string docs #23718

Job	Run time
Linux-32-bit	53s
Linux-Musl	14s
python-dev	0s
Pyodide build	53s
windows-latest actions-313.yaml	58s
macos-13 actions-312.yaml	56s
macos-13 actions-310.yaml	58s
macos-13 actions-313.yaml	58s
macos-14 actions-310.yaml	54s
windows-latest actions-310.yaml	11s
macos-14 actions-312.yaml	56s
macos-14 actions-313.yaml	54s
macos-14 actions-311.yaml	13s
windows-latest actions-311.yaml	56s
windows-latest actions-312.yaml	56s
macos-13 actions-311.yaml	58s
Pypy	14s
Locale: zh_CN	54s
ubuntu-24.04 actions-313.yaml	53s
Freethreading	53s
Minimum Versions	13s
Future infer strings	53s
ubuntu-24.04 actions-312.yaml	53s
ubuntu-24.04-arm actions-313.yaml	13s
Downstream Compat	53s
ubuntu-24.04 actions-310.yaml	13s
Numpy Dev	14s
Future infer strings (without pyarrow)	13s
Pyarrow Nightly	53s
ubuntu-24.04 actions-311.yaml	54s
ubuntu-24.04-arm actions-312.yaml	53s
ubuntu-24.04-arm actions-311.yaml	53s
ubuntu-24.04-arm actions-310.yaml	54s
Locale: it_IT	12s
	23m 6s

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